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Original question:

TL16C754C: TL16CP754CI SERIAL_IIR_RLS interrupt issue.

TL16C754C: 84AG1DN – TL16CP754CI - Lost communication

Chitransh Kulshreshtha
Intellectual 695 points
Part Number: TL16C754C

Hello TI,

I am using a TL16CP754CI part in my design for RS485 communciation.

The observation is that the part which is on board i.e., "84AG1DN – TL16CP754CI" is highly sensitive to the temperature change caused by radiated heat of surrounding components. around it. The communication is lost if i apply some heat over it using a hot air gun and once the gun is removed the communication starts up again.

Kindly suggest on if this is faulty date code part or guide further.

Do we have any errata document for the same??

PS.
Other parts with PN# "0BAF5W - TL16CP754CI" are working perfectly fine with the same arrangement.

Thank you.

  • 0
    TI__Guru 72751 points
    Hey Chitransh,

    Here is what I was told:

    "If the first one is 84AG1DW, this was manufactured in April 2018. 84AG1DN is not a real TI lot trace code.

    The second lot trace code is missing a character (should be 7 characters total). But assuming the first 2 characters listed are correct TI date code then the 0BAF5W was manufactured in November 2010."

    Do you know how hot the device is getting when you see failures?

    "Do we have any errata document for the same??"
    We don't for temperature.

    Thanks,
    -Bobby
  • 0 in reply to BOBBY
    Intellectual 695 points

    Hello Bobby,

    You are right about the correction of part number, it is 84AG1DW.

    About "Do you know how hot the device is getting when you see failures? "..
    Since it is mounted on board a very crude way of measuring temperature shows that the part stops communication as soon as the ambient temperature crosses 60-65 deg.C.

    Whereas I used another code part with "54A4KTW" which is mounted on a different board and this was working fine upto 90 Deg.C as expected.

    Both the boards have a similar PCB layout.

    Could u suggest any other way to narrow down on the cause of failure or some debugging tool that TI recommends?

    Thank you.

  • 0 in reply to Chitransh Kulshreshtha
    Intellectual 695 points

    Further investigation suggests that as soon as the temperature of the IC reaches ~60 Deg.C Pin39 - TXC of the IC is unable to transmit complete frame, missing some frames towards the end.

  • 0 in reply to Chitransh Kulshreshtha
    TI__Guru 72751 points
    Hey Chitransh,

    Can you provide an image of the PCB layout we could review?

    "Further investigation suggests that as soon as the temperature of the IC reaches ~60 Deg.C Pin39 - TXC of the IC is unable to transmit complete frame, missing some frames towards the end."
    Can you provide scopeshots of the TXC data packet from start to stop bit?

    What happens if you try to send more data? Does TXC still transmit or does it only mess up the ending bits of data?

    Thanks,
    -Bobby
  • 0 in reply to BOBBY
    Intellectual 695 points

    Hello Bobby,

    Attaching the snap for Full frame under normal operation with ambient temperature of ~25Deg C  and missing frame under ambient temp. at ~60 Deg C.

    For "What happens if you try to send more data? Does TXC still transmit or does it only mess up the ending bits of data?"


    Since the QUAD UART IC is mounted on board, I am not sure how to verify this as there are no provision to manually control the data to be send.

  • 0 in reply to Chitransh Kulshreshtha
    Intellectual 695 points

    Hello Boby,

    Attaching the snap of the PCB layout which shows the position of UART and track layout highlighted.

    Thank you.

  • 0 in reply to Chitransh Kulshreshtha
    TI__Guru 72751 points

    Hey Chitransh,

    Just to be clear, the values I specified in orange are expected values, correct? What you are concerned about is that you are missing a byte of data towards the end of the bottom waveform correct?

    Is the code between the top waveform and bottom waveform any different?

    If you add some delays in your parallel write sequences (Make IOW stay lower for a little longer or add some delay between instructions), will the last few bytes appear?

    Thanks,

    -Bobby

  • 0 in reply to BOBBY
    Intellectual 695 points

    Bobby,

    The Green values are expected values.
    Orange ones appear when the communication is lost.

    Per our design the 8-bit data bus for the QUAD UART is shared by another peripheral and there appears to be a hardware issue of signal reflection at higher temperature.
    when the bus was isolated the problem of communication appears to be solved.

    Thank you for your support.